The subject matter disclosed herein relates to a wireless communication protocol and an exemplary application of the wireless communication protocol implemented with respect to a system for magnetic resonance imaging (MRI) and computed tomography (CT) compatible wireless physiological gated imaging. More specifically, a system for obtaining physiological data of a patient, generating trigger signals for the MRI or CT scanner, and wirelessly communicating the physiological data and/or trigger signals in the MRI or CT environment is disclosed.
As is known to those skilled in the art, a magnetic resonance imaging (MRI) system alternately generates a strong magnetic field and then detects the faint nuclear magnetic resonance (NMR) signals given off by nuclei in the presence of the magnetic field. The NMR signals are received by antennas, also known as coils, and transmitted to the MRI scanner for reconstruction into an MRI image. In order to provide a clear image, it is desirable to minimize interference associated not only with external artifacts, such as electromagnetic interference, but also with motion artifacts, such as voluntary or physiologic motion.
As is also known to those skilled in the art, a computed tomography (CT) system takes a series of x-ray views of the desired object and reconstructs them to create cross-sectional images of the object. Many times, the tomographic slices may be combined to create 3-D images. A CT system relies upon x-ray particles being sent through the body and then detecting the amount of absorption or scattering of those particles to construct a representative image of the object based upon the density or other physical properties of the object or structure. Similar to an MRI scanner, a number of different artifacts may produce unwanted interference during a CT scan, such as motion artifact related to voluntary or physiologic motion.
Specifically, with respect to motion artifacts, MRI and CT imaging is complicated by the periodic motion of a patient, such as respiratory or cardiac motion. Cardiac motion includes, for example, motion of the heart and blood flow through blood vessels. Respiratory motion includes, for example, the expansion and contraction of the lungs and the resulting motion of the surrounding anatomy. Breath-holding is one technique utilized to minimize motion artifacts due to respiratory motion. However, due to the length of time required for some scans, breath-holding is not always practical. In addition, no such comparable technique may be employed to minimize cardiac induced motion artifacts.
However, much of the respiratory and cardiac induced motion is repeated over a certain cycle. Cardiac motion may be defined, for example, based on one cycle of an electrocardiogram (ECG). Respiratory may be defined on the basis of an inhalation/exhalation cycle. In order to reduce motion artifacts, certain points within each of the cycles may be identified. A peak value in the ECG or a maximum inhalation point may be identified. By obtaining successive images at the same point in the cycle, motion artifacts for the anatomy being imaged are reduced.
In order to trigger the MRI scanner or the CT scanner to obtain an image, however, a cycle must be measured and a trigger signal provided to the scanner to initiate image acquisition. The ability to reduce motion artifacts is impacted by the amount of time required between detecting the desired point in a cycle and initiating the image acquisition. The ability to reduce motion artifacts is similarly impacted by the repeatability of the amount of time, such that the anatomy being imaged is in the same relative position between images.
During imaging a number of physiological parameters of the patient may require monitoring. In order to reduce the number of cables and because cables may introduce artifacts as well, it is desirable to provide wireless sensors to monitor the physiological parameters of the patient. However, wireless communication may introduce transmission delays and/or repeatability issues between detecting the physiological parameter and transmitting the data.
Thus, it would be desirable to provide an improved transmission protocol for high reliability of transmission between wireless devices and, more particularly, for high reliability of transmission between wireless devices used for medical imaging.